RSS

How-To Geek

Zenity adds graphical interfaces to shell scripts with a single command. Shell scripts are a great way to automate repetitive tasks, but they’re normally confined to the terminal — Zenity brings them out of the terminal and onto your desktop.

We’ve given an introduction to shell scripting in the past. You don’t have to be a programmer to get started with shell scripts — they require little more than knowledge of Linux terminal commands.

Getting Zenity

Zenity comes with Ubuntu by default. If you use an Ubuntu derivative, Such as Kubuntu, you may have to install it manually with the following command:

sudo apt-get install zenity

Zenity is a part of GNOME, so it should already be included on Linux distributions that use the GNOME desktop. Check your package manager for the zenity package if you don’t have it.

Using Zenity

You can play around with Zenity from the terminal. Let’s say you want to create an error window when a problem occurs with your shell script. Here’s an example command you could use:

Catch the user’s input in a shell script and you could store it as a variable.

There’s also a file picker, calendar, and other types of dialogs. For a full list of dialog types and their options, consult Zenity’s manual page.

An Example Script

Let’s try using Zenity to create a simple graphical shell script. With just three commands, we can create a graphical timer program:

#!/bin/bash
# This script asks the user for a time, waits the specified amount
# of time, and shows an alert dialog.

TIME=$(zenity –entry –title=”Timer” –text=”Enter a duration for the timer.\n\n Use 5s for 5 seconds, 10m for 10 minutes, or 2h for 2 hours.”)

sleep $TIME

zenity –info –title=”Timer Complete” –text=”The timer is over.\n\n It has been $TIME.”

We’re using some extra tricks here. We get the value of the TIME variable from the first zenity command and feed it to the sleep command. We’re also using /n to create new lines of text in the zenity dialogs.

After saving the shell script and running the chmod +x command on it to give it executable permissions, we can launch it.

Enter a duration and the script will use the standard sleep command to count down in the background. When the sleep command’s timer finishes, the script will display the zenity info message.

You could create a desktop or panel shortcut for this script and run it without even touching the terminal.

This is just scratching the surface of what you could do with zenity; you could use it to make much more complicated programs. If you’re looking for more information on shell scripting, check out our guide to using for loops in shell scripts.

Shell scripting changes computing from
a) you doing things on a computer
to
b) the computer doing things for you.

Bash has many cool features. My nearly 1-stop how-do-I X in bash is the Advanced Bash-Scripting Guide – http://tldp.org/LDP/abs/html/ It isn’t about GUI/Zenity, but we all need to know this stuff to make computers of all sorts work FOR us.

A few really cool settings/options to make your bash scripts more bullet proof are:
* errexit
* pipefail
* trap
* nounset
* errtrace
and that you can declare variables to be read-only or integers. To learn more, here’s a copy of Michael Potter’s most excellent presentation: http://www.uniforum.chi.il.us/slides/bash1.pdf

I saw Michael give this presentation last month and I’m certain there were subtle things that I missed … even with 15+ yrs of shell scripting practice.

The dialog package (certainly the one provided with Debian/stable) runs fine in a terminal window. By default it uses “drawing” characters to present its box frames, but the –ascii-lines option forces it to revert to basic 7bit ASCII characters (+, -, |). Both methods appear to use the teminfo database to derive the appropriate positioning and drawing characters, which is a correct solution for something writing to a terminal.

A quick check of the libraries linked into dialog (ldd `type -p dialog`) also shows that ncurses is included, which is unsurprising given that it provides a much higher level interface than the raw terminfo library.

Hope this helps
Chris

DID YOU KNOW?

Despite the widely held misconception that the flush toilet was invented by Thomas Crapper, Crapper did not in fact invent the flush toilet but did, however, invent and patent several improvements that helped improve and modernize it.